A simple method for combining pore size distributions calculated from gas adsorption isotherms with mercury intrusion porosimetry

MicroActive 2.0 and MicroActive for 3Flex include a powerful utility for including the pore size distribution from mercury porosimetry analyses with pore size distributions calculated from gas adsorption isotherms. This new import function allows users to rapidly view micro, meso, and macro pore size distributions in one easy to use application.

Usage

This new import function has been added that allows users to rapidly include pore size distributions from other devices to be included into the standard Micromeritics sample file (SMP file). The pore size data from the external source such as a mercury porosimeter is imported from a simple text file. The first line of the text file includes a description, size units, quantity units, and type of data with the following format.


dataFile

Figure 1: Example file format for importing mercury porosimetry data.


<description> (<pore width units>, <quantity units>, <type>)
The porosimetry data then follows with the pore width in the first column and the quantity in the second column. An example of the format is given in figure 1. The intrusion data must be strictly increasing and extrusion data must be strictly decreasing.

description : used to identify the imported data and as the graph legend
pore width units : Ångstroms – A, nanometers – nm, or micrometers – um
quantity units : ml/g or cm3/g
type : incremental or cumulative

The incremental or cumulative data is available from the Micromeritics AutoPore 9500 application. The data may be copied by right-clicking on either the cumulative or incremental pore volume graphs generated by the AutoPore reports and then using the Copy as text option. A file to be imported is restricted to either intrusion or extrusion data. However, multiple files may be imported to allow the inclusion of both intrusion and extrusion data.

Importing pore volume data

The pore volume data may be integrated into a sample file (SMP file) using the Import … function located on the Report Options tab in the Advanced view of the SMP file (figure 2).


advanced

Figure 2: The import utility is found on the Advanced tab of the SMP file.


The Import … button opens a dialog, figure 3 and lists any pore volume data that have been previously imported to the SMP file and each set of pore volume data is listed by description. Additional data be be imported or removed from the SMP using the Select Imported Overlays dialog.


importFiles

Figure 3: The import file selector lists each pore size distribution by description.


If an error is encountered while importing the mercury porosimetry data, a descriptive message is displayed that includes a description of the correct file format, figure 4.


error

Figure 4: Error message for improperly formatted pore volume data file.


The imported data may then be used as an overlay with cumulative, differential, or log differential pore size distributions. The overlay is selected by editing the options for the BJH, Dollimore-Heal, Horvath-Kawazoe, and DFT pore size reports. Each report has the option for including an overlay and the Imported Data may be selected as seen in figure 5


bjhOVLY

Figure 5: Imported data may be used as an overlay in cumulative, differential, and log-differential pore size distributions.


Example

Commercial catalysts are commonly analyzed using nitrogen adsorption to determine surface area and porosity. The pore size distribution may then be calculated from the nitrogen adsorption isotherm using BJH. Mercury porosimetry is also commonly employed to determine the pore volume distribution of catalysts and the pore volume distribution may overlaid with the distribution calculated from the nitrogen adsorption isotherm.


bjhDovly

Figure 6: Overlay of BJH desorption, mercury intrusion, and mercury extrusion log differential pore size distributions for alumina pellets


In this example, the Micromeritics chemisorption reference material a 0.5 wt% platinum on alumina sample was characterized using nitrogen adsorption and mercury porosimetry. The nitrogen adsorption and desorption isotherms were used to calculate the pore size distribution using the BJH method. Both mercury intrusion and extrusion data were imported into the gas adsorption SMP file (figure 6).

The overlay of the pore size distributions is given if figure 6. Based upon this simple overlay of the log differential pore volume distribution, the size distribution (figure 6 in red) calculated from the desorption branch of the isotherm agrees well with the pores size distribution (in green) determined by mercury intrusion porosimetry.

Summary

MicroActive version 2.0 provides new and unique capabilities for integrating pore volume data from mercury intrusion analyses with the pore size distributions calculated from gas adsorption isotherms. The MicroActive software is compatible with SMP files from Micromeritics broad range of gas adsorption instruments and provides a new capability for examining new or historical pore volume distributions.